Sanitary napkins are generally comprised of at least two elements i.e. a fluid absorbing batt or layer and a fluid impermeable baffle to protect the undergarment of the wearer from leakage and/or fluid runoff from the absorbent batt. One of the problems associated with the design of the sanitary napkin is that a substantial portion of the absorbent material is not utilized due to the inability of the fluid to rapidly disperse through the absorbent matrix before local saturation of the absorbent material is complete. Also, during periods of high rates of flow, the fluid may be conducted along the surface of the absorbent material and/or a covering material placed over the absorbent component (the fluid pervious covering material used to maintain the integrity of the napkin) producing side leakage along the longitudinal edges of the napkin. The problems of localized saturation and side leakage have been treated independently in the past.
U.S. Pat. Nos. 3,294,091 and 4,200,103 disclosed the concept of extending the fluid impervious baffle up the sides of the absorbent batt and over the top surface of the napkin along each of the longitudinal edges thereof. The extension of the baffle onto the top surface of the absorbent component does seem to act to prevent side staining as long as a fluid barrier seal between the baffle and the cover material is maintained.
Conventional approaches to promotion of more even fluid distribution have been directed towards embossment patterns extending longitudinally along the length of the napkin. The theory behind the longitudinal embossment patterns is that the fluid would follow the embossment pattern lines which would tend to utilize the area between the surface of initial fluid contact and the edges of the napkin. Another approach to fluid distribution is disclosed in U.S. Pat. No. 3,230,955 which also provides for fluid distribution in the longitudinal direction but the distribution is accomplished by utilizing cellulose wadding material which had been laid in the machine direction producing fibers extending along the longitudinal direction. This tissue-like cover material when laid in the so-called machine direction, accomplished the same purpose as the longitudinal embossment lines.
Previously it has been thought necessary to convey fluid longitudinally to achieve enhanced absorbent utilization even though the fluid has a tendency to flow in all directions uniformly.
Another difficulty associated with the longitudinal directing of fluid is that, due to the nature of conventional cellulosic absorbent material used in napkins, very little of the bottom portion of the absorbent material is utilized. This is true because the top portion tends to become saturated and, as a result, discarded before the fluid migrates to the bottom portion of the absorbent batt. The sanitary napkin according to the teachings of this invention obtains superior absorbent capacity with superior fluid distribution while minimizing side staining.